The options of the question are, A) coal and oil. B) silver and machinery. C) oil and gold. D) iron and machinery.
The correct answer is D) iron and machinery.
Materials that had to be shipped to Central Pacific workers included iron and machinery.
For building the transcontinental railroad to link the United States from West to East, the materials that had to be shipped to Central Pacific workers included iron and machinery. With the Pacific Railroad Act of 1862, two companies had to work on the project; the Union Pacific Railroad and the Central Pacific. Both railroads finished the work when both companies rails met in Promontory, Utah in May 1869.